The invention relates to a method and a device for further processing of sheets to produce multi-page printed products, wherein several initial sheets are each folded into a folded sheet and subsequently collated one on top of the other such that the fold areas lie at the top and the folded sheets open downwardly, a groove being formed in each initial sheet before folding, around which groove the initial sheet is subsequently folded, the groove being widened, initial sheet by initial sheet, by a predetermined amount.
Such a method and such a device are known from EP 1 568 507 A1. The device described in this publication comprises a grooving means having two grooving wheels forming two parallel grooved lines in each initial sheet before folding, wherein an adjusting means controlled by a control means is provided, which adjusting means increases the distance between the grooving wheels gradually each time after the forming of grooved lines in a preceding initial sheet. The grooving of the initial sheets at a constantly increasing distance between the two grooved lines makes it possible to collate the folded sheets one on top of the other such that the folded sheets are able to lie planely one on top of the other in the spine area between the grooved lines and that the individual pages after the bonding thereof remain folded around clearly defined fold edges, resulting in a high-quality appearance of the finished printed product and in the fact that the individual folded sheets may be securely bonded, for example, by means of glueing. However, the construction of the known device is very expensive, since two grooving wheels are required, the distance between which has to be adjusted through the adjusting means.
The object underlying the invention is to provide a method and a device for further processing of sheets to produce multi-page printed products which make it possible, by means of a relatively inexpensive construction, to enable a high-quality appearance of the finished printed product.